Struct Message 

pub struct Message {
    pub sender: u64,
    pub reply_cap: u64,
    pub request_id: u64,
    pub tag: u16,
    pub payload: u64,
}

Fixed-size envelope carried in mailboxes and registers (Atomic Hop).

Why this exists (request-reply / typed protocols)

Receive delivers a single Value — not {sender, Value}. Without an envelope, a server flow cannot learn who sent a request, and two clients cannot safely share a request_id space.

Security

• sender: FlowId stamped by the scheduler on bytecode Send / Ask (invariant S1). Not a capability.
• reply_cap: CapId minted at the same boundary with SEND-only rights so the recipient can answer without ambient Pid addressing (phase 2). Zero means “no reply grant” (host-injected hops may omit it).

See docs/security.md.

Fields

sender: u64

Authenticated origin FlowId (0 = trusted host / non-flow).

reply_cap: u64

Capability granting SEND back to Self::sender, or 0.

request_id: u64

Client correlation token; echoed on replies (Ask / S2).

tag: u16

Protocol discriminator (opaque to the VM).

payload: u64

Small protocol payload.

Implementations

impl Message

pub const fn new(sender: u64, request_id: u64, tag: u16, payload: u64) -> Self

Build an envelope. sender / reply_cap are placeholders until a bytecode hop is authenticated by the scheduler (reply_cap typically 0 here).

pub const fn request(request_id: u64, tag: u16, payload: u64) -> Self

Outgoing hop from host Rust (sender / reply_cap filled on delivery).

pub fn reply_to(req: &Self, tag: u16, payload: u64) -> Self

Reply envelope echoing request_id from a received hop (host path).

pub const fn down(monitor: u64, target_flow: u64, reason: u64) -> Self

Runtime lifecycle hop: monitor DOWN (tag == TAG_SYS_DOWN).

sender is the dead flow’s identity (not a Cap). request_id is the crate::MonitorRef. payload is crate::FlowExitReason as u64.

pub const fn linked_exit(target_flow: u64, reason: u64) -> Self

Runtime lifecycle hop: Ask target exited (tag == TAG_SYS_EXIT).

Written into the Ask dest register when the callee dies before replying. payload is crate::FlowExitReason.

pub const fn is_down(self) -> bool

pub const fn is_exit(self) -> bool

Trait Implementations

impl Clone for Message

fn clone(&self) -> Message

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Message

impl Debug for Message

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Message

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Message

impl From<Message> for Value

fn from(m: Message) -> Self

Converts to this type from the input type.

impl Hash for Message

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Message

fn eq(&self, other: &Message) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Message